(a) Field of the Invention
The present disclosure relates to a cooperative spectrum sensing system using sub-Nyquist sampling and a method thereof. More particularly, the present disclosure relates to a cooperative spectrum sensing system, which allows a secondary (unlicensed) user renting frequency bands from a primary (licensed) user to detect an available frequency band, which is not occupied by the primary user, by using sub-Nyquist sampling, and a method thereof.
(b) Description of the Related Art
Federal Communications Commission (FCC) announced a research result that many parts of frequency bands are not used at the same time and they are very inefficiently used on time and space. To resolve a shortage of the frequency bands and to promote efficient utilization of the frequency bands, in recent, studies on cognitive radio networks (CRNs) have been actively conducted.
The cognitive radio networks are intelligent radio networks that allow a secondary (unlicensed) user renting frequency bands from a primary (licensed) user to timely access an available frequency band without causing disruptive interference with the primary user. To construct the cognitive radio networks, the secondary user needs to rapidly perform accurate broadband spectrum sensing for an unoccupied frequency band.
In the broadband spectrum sensing, sampling of very high speed should be performed to satisfy the Nyquist sampling rate, so an analog to digital converter (ADC) capable of performing the high speed sampling is necessarily required. However, since considerable cost is entailed to implement such an ADC, in practice it is nearly impossible to implement the broadband spectrum sensing as a hardware.
In detail, the broadband spectrum sensing may be basically divided into three fields: implement of the ADC for the Nyquist sampling, implement of a compressive sensing system, and implement of a sensing system using sub-Nyquist sampling.
However, the spectrum sensing system using the Nyquist sampling has a drawback that very expensive equipments such as a high-speed ADC should be prepared to construct such a system. In recent, accordingly, studies on construction of the compressive sensing system and the sensing system using the sub-Nyquist sampling have been more actively conducted.
In this case, the compressed sensing has very high complexity in a process of reconstruct signals compressed at a sampling rate lower than the Nyquist sampling rate to original signals, but the sub-Nyquist sampling has very low complexity in implementing an algorithm.
However, in the cognitive radio networks, there is a drawback that to obtain a closed form for sensing performance is impossible due to irregular occupancy of spectrum by the primary user and aliasing effect of the Nyquist sampling.
Korean Patent Publication No. 1189904 (published on Oct. 10, 2012) discloses a background technique of the present disclosure.